Morphogenesis of the Bacillus subtilis bacteriophage phi29 will be studied in the most efficient in vitro viral assembly system known. Protein conformational change and movement in particle assembly and DNA encapsidation will be investigated by the use of an integrated genetic, biochemical and biophysical approach. Cryo-electron microscopy and X-ray crystallography will provide a structural basis for direct measurement of the dynamic events of particle assembly. A complete model of phi29 morphogenesis will serve as a model for animal virus assembly and aid in the search for new antiviral therapies. Specifically, the structure of phi29 head assembly intermediates will be determined to sub-nanometer resolution by cryoelectron microscopy; atomic resolution structures of head assembly intermediates will be determined by X-ray crystallography; the structure and function of the gp16-pRNA complex of the phi29 packaging motor will be studied; the phi29 prohead will be assembled in vitro from purified proteins by the use of GroESL chaperonin and the putative Bacillus subtilis VAM chaperonin; structures of the isolated phi29 lower collar, neck appendage and tail protein oligomers, and their assembly to the DNA-filled head, will be studied by electron microscopy and X-ray crystallography; and selected phi29 mutants defective for DNA packaging or particle assembly will be characterized.